Democratic presidential candidate Martin O’Malley suggested Sunday that Congress had fallen under the sway of "white racism" and the political force of the National Rifle Assn. in refusing to respond with new laws to a cascade of shooting incidents in recent years.

Speaking before the nation’s mayors, gathered in San Francisco, O’Malley pointed to gun restrictions passed when he was governor of Maryland to ban assault weapons, enforce background checks and tighten permitting procedures -- efforts that have been blocked at the national level by Republicans, and some Democrats, in Congress.

"One of the sad triumphs of white racism is the degree to which it has succeeded in subconsciously convincing so many of us, black and white, that somehow black lives don’t matter," he said. "If the thousands of young men killed by gun violence every year across America were young, poor and white -- rather than young, poor and black -- it is hard to imagine that our Congress would continue to block common-sense measures to keep guns out of the hands of criminals."

"How many acts of violence do we have to endure as a people before we stand up to the congressional lobbyists of the National Rifle Assn.? How many more Americans have to die?" he added, ticking off killings at an elementary school in Newtown, Conn., a theater in Aurora, Colo., and the Navy Yard in Washington, D.C.

O’Malley, a familiar face to the mayors since his pre-gubernatorial tenure as mayor of Baltimore, was the third national Democrat to use the gathering to call for restrictions on the availability of guns in the wake of Wednesday’s mass shooting at Emanuel African Methodist Episcopal Church in Charleston, S.C.

President Obama on Friday and Democratic presidential candidate Hillary Rodham Clinton on Saturday also demanded changes that have been forwarded in recent years but then foundered.

Clinton delivered an evocative call to personal and political reflection on racial matters, and O’Malley also walked that ground when he mocked South Carolina’s use of the Confederate flag. He contrasted its continued acceptance to the forgiveness that the Charleston victims’ families offered the accused shooter in court on Friday.

"What a terribly jarring and callous sign then, in the wake of this racist massacre, to see the American flag at half-staff while above it, at full-staff over the state Capitol of South Carolina, flew a Confederate flag," he said. "Families in Charleston can forgive.... Is it really too much to ask the state government officials of South Carolina to retire the Confederate flag?"

(Contrary to O’Malley’s assertion, the Confederate flag flies on the grounds of the state Capitol, not atop it. An American flag there flew at half-staff after the shootings.)

O’Malley was an early entrant into a presidential race in which he remains a severely cobbled underdog to Clinton. At the mayor’s conference, the power imbalance was clear: Before his speech, the organization aired a video of previous events that prominently featured pictures of Clinton, who unlike O’Malley was mobbed by the mayors after her speech.

The former governor made no mention of his opponent and barely any mention of Obama as he talked about the unfinished national business on which he is resting his campaign. He has the same touchy task as Clinton: to acknowledge the failings of the Obama years without repudiating a president who remains highly popular among their party’s voters.

O'Malley said he would lead a renaissance of job creation in the nation’s cities -- although he did not say how, other than to insist that it had to be done by the president, not state or local leaders.

"For all the good work President Obama has done to save us from the second Great Depression," he said, "… the fact of the matter is most Americans feel like we are all working harder but slipping further behind -- and they’re not wrong."

The sentiment is one that Clinton has addressed as well and stands to put forward in a campaign far heftier than O’Malley will be able to command. He underscored that with a final plea to the mayors: